Field of Invention
The invention relates to a piezoelectric speaker driving system, and particularly relates to a piezoelectric speaker driving system and method that may improve the sound pressure level of a sound form a piezoelectric speaker.
Description of Related Art
The principle of operation of a piezoelectric speaker is very different from that of the traditional coil driven speaker. According to the traditional coil driven speaker technology, the coil is provided in an external magnetic field and is attached to a diaphragm. When an electric current is passed through the coil, a magnetic field is created around it and under interaction with the external magnetic field reacts, so as to generate a mechanical vibration to the diaphragm and excite acoustic airwave. In other words, the electric energy is first converted to the magnetic energy, and then is converted to the mechanical force on the diaphragm to generate sound. On the other hand, in the piezoelectric speaker a piezoelectric material is attached to a diaphragm. When a voltage is applied across the piezoelectric material, its flexure or dimensional movement is transferred to the diaphragm to excite acoustic airwave. That is, the electric energy is directly converted to the mechanical force on the diaphragm to generate sound, such that the piezoelectric speaker has improved energy conversion efficiency compared with the traditional coil driven speaker. Therefore, the piezoelectric speaker is widely used in the portable devices. However, the piezoelectric material has a relatively poor frequency response of sound pressure level, particularly at the lower frequency band, in view of the coil driven speaker.
Typically, different ways of making and attaching a structure between the piezoelectric material and the diaphragm are used to address the above issues of the piezoelectric speaker. However, the structure is easily subjected to the influence of the whole structure of the piezoelectric speaker. Therefore, there is a need for a user to improve the sound pressure level of the piezoelectric material at the lower frequency band.